Many bicycles are equipped with gear shifting mechanisms to match the limited power of the human operator to the terrain and to the desires of the operator for speed. Most commonly, manual systems are used to move the driving chain to larger or smaller sprockets connected to the driving hub of the wheels of the bicycle. Less commonly, gearing has been disposed inside the hub itself to obtain the desired ratio of pedal revolutions to wheel revolutions.
Some of these hub gearings are manually activated and some are speed responsive. While many bicycle operators desire maximum speed to govern the gear ratio of pedal to wheel, others desire to use the output of human energy to control the shifting and thereby accommodate to hills, soft ground and other features by changes in gear ratio. While this automatic torque response shifting is widely desired there have been few hubs available on the market.